This invention relates in general to measuring devices and in particular to a new and useful measuring head which includes a feeler pin mounted in a casing for movement in three-dimensional directions relative to a stationary frame structure.
There are known measuring heads comprising a feeler pin which is three-dimensionally movable relative to a fixed frame construction and, by moving into measuring contact, is displaced in accordance with the design of the parallelogram structure of the measuring head. Such a construction which permits a parallel displacement of the feeler pin in all directions of the X, Y, Z coordinate system is desirable, yet also expensive and requires space which is frequently not available. In one prior art design, the measuring head comprises a system of plates which are superposed in spaced relationship and in which leaf springs are attached between the lowermost two plates, for deflection in the X direction and between the superjacent next two plates, for deflection in the Y direction. Thereabove, space two plates have angled lateral wall extensions between which leaf springs deflecting in the Z direction are inserted. Within the arrangement of plates, a measuring system for evaluating the measurement, and elements for returning the feeler pin into its coordinate zero position, are provided. Even though this system, due to the parallelogram, construction, advantageously ensures a substantially parallel displacement of the feeler pin at the measuring contact with the workpiece, the arrangement is too expensive and the space this sandwich structure requires in the vertical direction is excessive.
A measuring head of different design is disclosed in German AS No. 38 04 398. In this measuring head, intended for a coordinate measuring machine, the feeler pin is mounted in a casing, by means of a bearing system of balls, for tilting in any direction and for being vertically removed. The tilting of the feeler pin relative to its bearing structure is effected against the action of a spring by which the pin is returned into its initial position after each deflection.